This invention relates generally to a manually actuated liquid pump dispenser having a pump plunger with a stem reciprocable through a collar of the pump and normally rotatable about the longitudinal axis of the plunger, the dispenser having means for locking the plunger in its fully depressed position for shipment and storage. More particularly, the invention relates to a removable tamper evident lock element in the form of an arcuate strip for retaining the plunger in its fully depressed locked position.
A dispenser of the general class to which the present invention is directed is disclosed in U.S. Pat. No. 3,062,416 in which the plunger head is externally threaded for threaded engagement with the internal threads of a collar on the pump for locking the plunger in its fully depressed position upon plunger rotation in a given direction, such as clockwise. The dispenser is typically shipped and stored in such lock-down position such that prior to use the plunger must be unthreaded from the collar in readiness for pumping.
Another pump dispenser having a plunger lock down feature is disclosed in U.S. Pat. No. 4,479,589 in which the plunger is provided with spaced radial lugs corresponding to lug receiving notches located in the collar and a corresponding series of shoulders interspersed between the notches. With the notches and lugs in registry the plunger may be depressed and locked in its fully depressed position upon plunger rotation to dispose the lugs beneath and in engagement with the shoulders.
The plunger lock-down dispensers of the foregoing type prevent loss of liquid during handling and shipping as the container is completely sealed. However, the ease in unlocking the plunger by unthreading it from its collar invites tampering while especially on the store shelf by someone who would surreptitiously sample the product by simply unthreading the plunger and pumping the liquid product into the hands for a free sample.
Otherwise, children have been known to unlock the dispenser and pump the liquid onto the floor or elsewhere in the store creating a safety or health hazard. Moreover, during shipment, the plunger can unthread itself loose from its collar thereby causing product leakage in the shipping carton.